Fuel gauge bouncing. Normal?

[Outnumbered]

Ok, I am still learning. Maybe someone with more experience could answer this question?
I just installed a fuel pressure gauge on my 800 Holley dual feed. The gauge is reading (bouncing between) 4.5-5.5 lbs at idle and about the same at 2,000 rpm. The gauge is bouncing. Is this normal? The engine is running pretty smooth and the gauge is mounted solid. I am running a stock mechanical fuel pump (original I think) on a 1987 Ford 460, 340hp. I have been having some higher RPM misfire and surging and wonder if the fuel pressure may be an issue? :confused:
Thanks is advance for the help,
OL

[Rexone]

Old Lavey:
Ok, I am still learning. Maybe someone with more experience could answer this question?
I just installed a fuel pressure gauge on my 800 Holley dual feed. The gauge is reading (bouncing between) 4.5-5.5 lbs at idle and about the same at 2,000 rpm. The gauge is bouncing. Is this normal? The engine is running pretty smooth and the gauge is mounted solid. I am running a stock mechanical fuel pump (original I think) on a 1987 Ford 460, 340hp. I have been having some higher RPM misfire and surging and wonder if the fuel pressure may be an issue? :confused:
Thanks is advance for the help,
OL Fuel pressure cycling like this isn't that unusual with a mechanical pump especially when no regulator is involved. However your 4.5 to 5.5 psi at idle to 2000 rpm might be a sign for concern. The fact that it's not greater than 5.5 @ 2000 tells me that's it's capacity (or you have a regulator you haven't mentioned that's set too low). Typically fuel requirements go up from there and your pressure may drop further which would explain your higher RPM problem. Most Holleys will handle 7 lbs at the needle valve and that's a good number to aim at to avoid fuel starvation. I run 8-9 lbs with good needle valves on a twin turbo application and it will drop to 6-7 on sustained hard running. I don't like to see it much lower than that for any length of time. I run a guage right on the dash in this particular boat because adequate fuel pressure is a must. I've actually shut her down based on inadequate fuel pressure in the past. That was with Holley Blue pumps in the equation. Have since changed to Mallory 140's and no more of those problems since.
Hope some of that helps you. :)

[Wet Dream]

I might be wrong, but is it a liquid filled gauge? The vibrations from the engine might be enough to get it to bounce. Liquid filled gauges keep this from happening and will last longer.

[Thunderbutt]

If it is from vibration maybe you need a liquid filled gauge. 4.5 to 5.5 is still too low.

[Outnumbered]

Thanks for the replies.
No regulator.
It isn't liquid filled. The gauge is steady, its not bouncing from movement.
It seems to be pulsing rapidly with the motor RPMs. Unfortunately I didn't check the fuel pressure before this problem started so I don't know what it was running last year (before the problem). I have been running this set-up for 3 seasons now without a problem. This new problem started the first trip of this season. When I put it away last year it was running perfect. I think I will replace the fuel pump and see if that helps.
Thanks again,
OL
[ April 27, 2003, 09:35 PM: Message edited by: Old Lavey ]